1.10: The Circle of Fifths

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10.1 Introduction

\[\hat5\]

In this chapter we will discuss the various types of relationships that occur between keys. We will introduce a widely-used diagram known as the circle of fifths to provide a visual representation of these relationships.

10.2 The circle of fifths

The following diagram arranges the sharp keys around the edge of a circle. (The accidentals for each corresponding key signature are also indicated.)

Example 10–1. The circle of fifths, sharp keys only.

example_10-1

This diagram, commonly referred to as the circle of fifths, is a useful way of visualizing key relationships. The diagram gets its name from the fact that as we move clockwise around the circle, each new key is built on the fifth scale degree of the one that came before it. C major is placed at the top of the diagram because it requires no accidentals. Each clockwise step also adds one more sharp to the key signatures. Moving from D major to A major, for example, requires the addition of one more sharp:

Example 10–2.

a. D major key signatures

example_10-2a

b. A major key signatures

example_10-2b

We can add flat keys to the circle as well. Increasingly flat keys will move counterclockwise around the circle:

Example 10–3. The circle of fifths, all major keys.

example_10-3

\[\hat4\]

Example 10–4.

a. Eb major key signature

example_10-4a

a. Ab major key signature

example_10-4b

\[\hat4\]

Note: As discussed in Chapter 8, there are several handy tricks for quickly figuring out the tonic of a key based on its key signature. For sharp keys, the right-most accidental of the key signature is the leading tone of the key. For flat keys, the right-most accidental of the key signature is scale degree $\hat4$ in that key.

Notice as well that there is some overlap at the bottom of the circle. These keys—which tend to be used less frequently than those with fewer accidentals—are enharmonically equivalent. C# major and Db major, for example, both begin on the same pitch class, but are spelled differently.

You should be familiar enough with the relationships between major keys and their key signatures to be able to reproduce the circle of fifths from memory.

Activity 10-1

Activity 10–1

Answer the following questions using the circle of fifths,

Exercise 10–1a:

Question

How many pitch classes do A major and E major have in common?

Hint

How many steps around the circle are there between these two keys? Each step represents one different pitch.

Answer

Exercise 10–1b:

Question

How many pitch classes do F major and G major have in common?

Hint

How many steps around the circle are there between these two keys? Each step represents one different pitch.

Answer

Exercise 10–1c:

Question

How many pitch classes do Eb major and A major have in common?

Hint

How many steps around the circle are there between these two keys? Each step represents one different pitch.

Answer

Exercise 10–1d:

Question

How many pitch classes do Bb major and D major have in common?

Hint

How many steps around the circle are there between these two keys? Each step represents one different pitch.

Answer

10.3 Minor keys and the circle of fifths

Minor keys can be added to the circle as well. Each minor key is paired with its relative major (the key with which it shares a key signature). A minor, therefore, is placed at the top of the circle, paired with C major because it, too, has no sharps or flats in its key signature:

Example 10–5. The complete circle of fifths.

example_10-5

\[\hat5\]

\[\hat2\]

10.4 Summary

All keys, major and minor, can be arranged on a circle of fifths to show the relationships between them. Relative keys are paired together because they share the same key signature. C major and A minor, for example, appear at the top of the circle and have no accidentals in their key signatures.

\[\hat5\]

The circle of fifths is particularly useful in showing the closeness of various keys with regards to their key signatures. C major and G major are closely-related, differing by only one pitch class. C major and F# major, on the other hand, are not closely-related and differ by six pitch classes. It is important to keep in mind that parallel keys, while not adjacent on the circle of fifths, are heard as related because they share the same tonic.